diff --git a/lib/superfox/qpc_decode2.f90 b/lib/superfox/qpc_decode2.f90
index 2a260e021..7900cb7ee 100644
--- a/lib/superfox/qpc_decode2.f90
+++ b/lib/superfox/qpc_decode2.f90
@@ -149,16 +149,17 @@ subroutine smo121a(x,nz,a,b)
   return
 end subroutine smo121a
 
-subroutine remove_tone(c0,npts)
+subroutine remove_tone(c0,fsync)
 
+  parameter (NMAX=15*12000)
   parameter (NFILT=8000)
-  complex c0(npts)
+  complex c0(NMAX)
   complex cwindow(15*12000)
-  complex cref(npts)
-  complex cfilt(npts)
+  complex cref(NMAX)
+  complex cfilt(NMAX)
   real window(-NFILT/2:NFILT/2)
 !  real endcorrection(NFILT/2+1)
-  real s(npts/4)
+  real s(NMAX/4)
   integer ipk(1)
   logical first
   data first/.true./
@@ -166,7 +167,7 @@ subroutine remove_tone(c0,npts)
 
   if(first) then
     pi=4.0*atan(1.0)
-    fac=1.0/float(npts)
+    fac=1.0/float(NMAX)
     sumw=0.0
     do j=-NFILT/2,NFILT/2
       window(j)=cos(pi*j/NFILT)**2
@@ -175,37 +176,60 @@ subroutine remove_tone(c0,npts)
     cwindow=0.
     cwindow(1:NFILT+1)=window/sumw
     cwindow=cshift(cwindow,NFILT/2+1) 
-    call four2a(cwindow,npts,1,-1,1)
+    call four2a(cwindow,NMAX,1,-1,1)
     cwindow=cwindow*fac        ! frequency domain smoothing filter
     first=.false.
   endif
 
   fsample=12000.0
-  df=fsample/npts
-  fac=1.0/npts
+  df=fsample/NMAX
+  fac=1.0/NMAX
   cfilt=fac*c0
-  call four2a(cfilt,npts,1,-1,1)   ! fourier transform of input data
-  iz=npts/4
+  call four2a(cfilt,NMAX,1,-1,1)   ! fourier transform of input data
+  iz=NMAX/4
   do i=1,iz
      s(i)=real(cfilt(i))**2 + aimag(cfilt(i))**2
   enddo
 
-  ia=nint(700.0/df) 
-  ib=nint(800.0/df) 
+  ia=nint((fsync-100.0)/df) 
+  ib=nint((fsync+100.0)/df) 
   ipk=maxloc(s(ia:ib))
   i0=ipk(1) + ia - 1
-  f2=df*i0
-  write(*,*) 'remove_tone - frequency: ',f2
+
+  i10=nint(10.0/df)
+  ia=i0-i10
+  ib=i0+i10
+  s0=0.0
+  s1=0.0
+  s2=0.0
+  do i=ia,ib
+    s0=s0+s(i) 
+    s1=s1+(i-i0)*s(i)
+  enddo
+  delta=s1/s0
+  i0=nint(i0+delta)
+  f2=i0*df
+
+  ia=i0-i10
+  ib=i0+i10
+  do i=ia,ib
+    s2=s2 + s(i)*(i-i0)**2  
+  enddo
+  sigma=sqrt(s2/s0)*df
+
+!  write(61,*) 'frequency, spectral width ',f2,sigma
+  if(sigma .gt. 2.5) go to 999
+!  write(61,*) 'remove_tone - frequency: ',f2
 
   dt=1.0/fsample
-  do i=1, npts
+  do i=1, NMAX 
     arg=2*pi*f2*i*dt
     cref(i)=cmplx(cos(arg),sin(arg))
   enddo    
   cfilt=c0*conjg(cref)   ! baseband to be filtered 
-  call four2a(cfilt,npts,1,-1,1)
+  call four2a(cfilt,NMAX,1,-1,1)
   cfilt=cfilt*cwindow
-  call four2a(cfilt,npts,1,1,1)
+  call four2a(cfilt,NMAX,1,1,1)
 
   nframe=50*3456
   do i=1,nframe
@@ -213,6 +237,6 @@ subroutine remove_tone(c0,npts)
     c0(i)=c0(i)-cref(i)
   enddo
 
-  return
+999  return
 
 end subroutine remove_tone
diff --git a/lib/superfox/sfrx_sub.f90 b/lib/superfox/sfrx_sub.f90
index b0e1dcb92..0779b23ef 100644
--- a/lib/superfox/sfrx_sub.f90
+++ b/lib/superfox/sfrx_sub.f90
@@ -36,6 +36,8 @@ subroutine sfrx_sub(nyymmdd,nutc,nfqso,ntol,iwave)
 
   call sfox_ana(dd,npts,c0,npts)
 
+!  call remove_tone(c0,fsync)  ! Needs testing
+
   ndepth=3
   dth=0.5
   damp=1.0